To start with, you're fighting an uphill battle. All cars (in stock form) will understeer. They are designed that way because it's safer. Understeer leads to spins and complete loss of control. With understeer, you always have some amount of control of the car and the bonus that you can see where you're going.

I'm not really much of a FWD guy, so I can't really answer whether it would be beneficial for your car.
It was an absolute necessity in my mustang. Of course mustangs (pre05) can't turn to begin with. In that car, I could actually use trailbraking to rotate the back end on entry and power to rotate it on exit.
When I drove Jesse's MR2, I was coming into a turn way too hot and trailbraked out of pure instinct. It came around on me in a heartbeat.
The FFR doesn't react well to it either. I can get away with a VERY limited amount of trailbraking, but the even weight distribution and short wheel base make it very difficult to manage and in all reality thus far, I've found it faster to just slow down to a speed that I can take the turn at and accelerate out.

Back to the scion. I'd imagine it might be able to help a little, BUT I don't know that it'll buy enough corner speed to be worth it... As always, slow in, fast out works.